After her friend Eichi moves to America without knowing her true feelings, Mitsuki Kouyama embarks on a journey to become a singer despite battling throat cancer. Determined to uphold their shared dreams, she rejects surgery that could silence her voice. When two shinigami, Meroko Yui and Takuto Kira, reveal she has only a year to live, Mitsuki teams up with them to pursue her music aspirations. Full Moon wo Sagashite delves into Mitsuki's poignant tale of resilience, friendship, and the pursuit of life through song.